FLUX DECLINE BEHAVIOR WITH LOW-MOLECULAR-WEIGHT SOLUTES DURING ULTRAFILTRATION IN AN UNSTIRRED BATCH CELL

Experimental studies were carried out on the flux decline behaviour of various solutes during ultrafiltration (UF) in an unstirred batch cell. A theoretical model was developed to predict the flux decline pattern during UF using the integral model as well as the resistance in series model. The model was found to predict the flux profiles during UF of low and high molecular weight solutes quite accurately. The model was further compared to other theories from literature which showed departure for the case of low molecular weight solutes. The model describes the UF flux behaviour of PEG-6000 as well as that of PVA in an unstirred batch cell. Thus, it may serve to predict the limiting flux phenomena during UF of low molecular weight solutes as well as that of high molecular weight solutes. These predictions may be useful in modelling the UF system. It was found that for high molecular weight solutes, a gel-layer was formed after some finite time. The model was tested with experimental flux values at high pressures for different solutes [black liquor, polyethyleneglycol and poly (vinyl alcohol)] and the results were found to be in good agreement.